/*******************************************************************************
 * Copyright 2014 United States Government as represented by the
 * Administrator of the National Aeronautics and Space Administration.
 * All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/
package gov.nasa.ensemble.common.collections;

import gov.nasa.ensemble.common.logging.LogUtil;

import java.util.Comparator;

/**
 * This default comparator tries to compare two objects using
 * their Comparable methods, if the objects implement that
 * interface.  Otherwise, it falls back on the 
 * EncounterOrderComparator.
 * 
 * @author abachmann
 *
 * @param <T>
 */
public class DefaultComparator<T> implements Comparator<T> {

	public static DefaultComparator<Object> INSTANCE = new DefaultComparator<Object>();
	
	@Override
	public int compare(T o1, T o2) {
		if (o1 instanceof Comparable) {
			Comparable comparable = (Comparable) o1;
			try {
				return comparable.compareTo(o2);
			} catch (ClassCastException e) {
				// reasonable
			} catch (Exception e) {
				LogUtil.error("bad comparable 1", e);
			}
		}
		if (o2 instanceof Comparable) {
			Comparable comparable = (Comparable) o2;
			try {
				return -comparable.compareTo(o1);
			} catch (ClassCastException e) {
				// reasonable
			} catch (Exception e) {
				LogUtil.error("bad comparable 2", e);
			}
		}
		return EncounterOrderComparator.INSTANCE.compare(o1, o2);
	}

}
